Annealing and cleaning cold rolled strip steel



Aug. 16, 1949. w. B. COOPER EI'AL 2,473,964

ANNEALING AND CLEANING COLD ROLLED STRIP STEEL V Filed Nov. 24, 1944 s Shets-Sheet 2 Edward J: Jeabvld Aug. 16, 1949.

Filed Nov. 24, 1944 w. a. COOPER ET'A L ANNEALING AND CLEANING COLD ROLLED STRIP STEEL 6 Sheets-Sheet 3 ANNEALING AND CLEANING GOLD ROLLED STRIP STEEL Filed Nov. 24, 1944 6 Sheets-Sheet 4 w @1111 aw vm,

Aug.1e,1949. w. B. CQ PE'R Em 2,478 4 ANNEALING AND CLEANING COLD ROLLED STRIP STEEL Filed NOV. 24, 1944 6 Sheets-Sheet 5 JII:

: mm! 13.9 13 L137 n I n 1 III iiii I i 0 c illjf' a lll I In .142 l wt I l 01 o I 0 Aug. 16, 1949. w. a. COOPER ETAL 2,478,964

ANNEALING AND CLEANING COLD ROLLED STRIP STEEL 6 Sheets-Sheet 6 Filed Nov. 24, 1944 Patented Aug. 16, 1949 UNITED STATES PATENT OFFICE ANNEALING AND CLEANING COLD ROLLED STRIP STEEL .William B. Cooper and Edward J. Seabold, Baltimore, Md, assignors to Crown Cork & Seal Company, Inc., Baltimore, Md., a corporation of New York Application November 24, 1944, Serial No. 565,014

9 Claims. 1

' paratus for continuously handling and annealing strip steel.

More particularly, the invention is concerned with means for and methods of continuously bright-annealing low carbon, cold rolled strip steel.

It is an object of the invention to provide an improved continuous annealing method to take the place of conventional batch annealing processes, thereby to improve the quality and uniformity of the anneal, as well as to shorten the annealing time and reduce its cost.

It is a further object to increas the tonnage of strip steel that may be annealed in a given length of time with an apparatus occupying a particular area of plant space.

It is a further object of the invention to reduce greatly the cost of annealing strip steel, by ma terially reducing the heating costs, the handling costs and other labor charges.

It is a further object of the invention to produce in the strip steel an improved anneal, characterized by small, uniform grain structure, resulting from the use of high annealing temperatures followed by rapid cooling irom the critical temperature tosubstantially room temperature. In accordance with the invention, the material is maintained at a high annealing temperature for a sufficient period of time to permit the crystalline grains to lose the orientation and elongated shape acquired in cold rolling, and to assume the random positions characteristic of well-annealed steel, but the steel is cooled with suflicient speed to prevent the formation of large grains of ferrite, which is a characteristic result of the long cooling periods used in batch annealing.

It is a further object of the invention to provide novel, improved means for accurately and uniformly controlling the temperature to which the strip is raised during its treatment, the time during which the strip is held or soaked at a high temperature, and the time, rate and degree of cooling.

It is a further object of the invention to provide novel means for preventing or controlling oxidation of the strip during the annealing process, whereby a bright-annealed strip or a strip having desired, controlled color characteristics, may be produced.

One of the principal objects and advantages of the present invention is the elimination, in a continuous annealing method, of fluctuations in the temperature to which the striga is subjected, whereby inequalities in the ductiluty and hardness of the annealed strip are eliminated. Thus, the invention includes novel methods of maintaining the heating means and the strip passing through particular zones of the furnace at desired constant temperatures.

It is a further object of the invention to provide novel methods of controlling the hardness and ductility of the annealed strip, by controlling and varying the temperature in the soaking zone and the cooling rate.

A further object of the invention is to provide improved methods of and apparatus for cleaning th palm oil, employed in the cold rolling operation, from the surfaces of the strip steel. Another object is to eliminate the use of expensive apparatus and costly chemicals in the cleaning of palm oil from strip steel, thereby entirely eliminating the cost of preliminarily cleaning the steel, prior to annealing, which heretofore has always been necessary. For instance, in batch annealing processes, the cost of cleaning the palm oil from the strip amounts to about $1.10 per ton, and the oil and cleaning chemicals are entirely wasted.

A further object of the invention is to convert a cleaning operation from a liability into an asset, by reducing the electric current consumption required to raise the steel to the annealing temperature. To this end, the invention contemplates burning the palm oil from the strip steel in the heating chamber and using the heat generated during the combustion of the palm oil to assist, at least in part, in raising the temperature of the strip to the annealing temperature.

A further object of the invention is to burn the palm oil from the strip steel, to clean the latter, without destroying the non-oxidizing character of the atmosphere in the annealing and cooling chambers.

A further object is to improve the heat absorptive characteristics of the strip steel by introducing it into the heating chamber with its surfaces in a dull, non-reflective condition, because of the presence of a film of palm oil thereon.

It has been discovered that, because of the dull,

3 oiled condition of the surface of the strip, it has approximately two and one-half times the heat absorptive qualities of a bright, dry reflective strip, previously cleaned in an alkaline solution.

A further object of the invention is to so regulate the burning of the palm oil on the surfaces of the strip-that a clean, complete and eflicient combustion takes place, leaving substantially no carbon deposit in the heating chamber, but without introducing an excess of oxygen, which would adversely afiect the non-oxidizing character of the atmosphere.

Other objects and advantages of the invention will be apparent from a consideration of the following description of certain specific embodiments of the invention shown in the accompanying drawings.

In the drawings:

Figure 1 is a side elevation of a preferred form of annealing apparatus with certain parts removed for the sake of clarity, and with certain parts shown somewhat diagrammatically;

Figure 2 is a vertical section view of the heating section of the annealing furnace of Figure 1, on a somewhat enlarged scale, with certain parts removed and other parts broken away;

Figure 3 is a transverse sectional view taken on line 2-3 of Figure 2;

Figure 4 is a top plan view of the apparatus in Figure 1 with certain parts removed;

Figure 5 is an enlarged fragmentary vertical section through one of the heating chambers showing a preferred arrangement of heating elements;

Figure 6 is a sectional detail, showing a preferred terminal arrangement;

Figure 7 is a vertical sectional view of one of the caps or hoods for closing the upper end of one of the heating chambers;

Figure 8 is a horizontal sectional view showing the furnace floor in plan;

' Figure 9 is a side view, on an enlarged scale,

partly in section and partly in elevation, showing the lower end of the furnace structure and the strip guiding means;

Figure 10 is a fragmentary vertical section taken on line I0-I0 of Figure 9;

Figure 11 is a plan view of the furnace casing, with the brickwork, guiding rolls and closure hoods removed;

Figures 12 and 13 are sectional details taken on corresponding section lines on Figure 11;

Figure 14 is a plan view of a channel-forming frame member or collar adapted to be mounted at the upper ends of the side walls of the furnace casing;

Figure 15 is an end elevation of the member shown in Figure 14, while Figures 16 and 17 are sections on corresponding section lines on Figures 14 and 15;

Figure 18*is a plan view of the hood or cap shown in Figure 7, while Figures 19 and 20 are an elevation and a vertical section thereof, the latter being taken on line 20-20 of Figure 19;

Figure 21 is a vertical sectional view of a gastight roll seal through which the strip passes to the annealing apparatus, and

Figures 22 and 23 are side and front elevational views of the apparatus of Figure 21.

As explained in detail in the above identified applications. the strip steel I0 is drawn from any suitable source of supply, such as one of a plurality of coils of strip, through a looper I0, a heating furnace H9 anda plurality of cooling chutes, in which the strip is reduced to a non-oxidizing temperature before it is exposed to the atmosphere. The strip passes beneath a guide roll 90 and then through a looper, as explained in the above identified applications and to a reeling device. Master pinch rolls may be interposed between the guide roll and the looper on the discharge side, to draw the strip through the apparatus, as described in those applications.

On its way to the furnace, the strip passes to the first one of a plurality of lower rolls II of the looper I0, the rolls being journalled on a fixed lower frame I2. A plurality of upper rolls I3 are journalled on a vertically movable frame I4, supported by cables 15 and an appropriate counterweight, not shown. The strip passes over the several rolls in a serpentine path, to provide a reserve supply of strip between the main supply, constituted by a plurality of coils, and the entrance guide roll I6 of the annealing furnace, to permit the strip, behind the looper I0 to be stopped while the leading end of a new coil of strip is welded to the trailing end of an exhausted coil, while permitting a continuous delivery of strip from the looper to the annealing furnace. It will be understood that, while the delivery of strip to the looper is arrested, to permit the making of such a weld, the upper frame I! of the looper is drawn downwardly against the action of its counterweight, to permit the continuous delivery of strip to the furnace. As scones the welding has been completed, the strip is delivered to the looper at a speed above normal, to replenish the supply in the looper, while contimring the delivery of the strip to the furnace.

The furnace proper is supported by a suitable framework comprising upright structural members "5, a lower platform H0, and upper. horizontal frame members I". The frame may be braced by suitable tie rods 8, or the like. The platform H6 supports the furnace casing 0 made up of a plurality of relatively heavy sheet metal sections continuously welded along their meeting edges and reinforced by suitable angle bars and the like to provide a strong, substantially gas-tight casing structure. Referring to Figures 2, 3, 5, 8 and 9, within the casing II! and supported by the platform Hi, there is a refractory brickwork floor I20, and similar side walls I2I, I22, front and back end walls I22 and vertically extending partitions I24, I25 and I2, providing four vertical heating chambers I21, I20, I20 and I30. The floor I20 is provided with a plurality of relatively narrow openings I210- I30a, registering, respectively, with the vertical furnace chambers. At their upper ends, the chambers terminate in restricted throats I21?)- I30b, respectively, which communicate with roll chambers I 3|, I32, lined by continuations of the side and end walls and the vertical partition 12!.

The space between the brickwork walls I2I, I22 and I23 and the metal furnace casing II, is packed with suitable heat insulating material.

such as rock-wool, asbestos, or the like.

newness flat, horizontally disposed plates I 31, providing two rectangular bases (Fig. 1'1) for rectangular, channel-forming collars I38, one of which is shown in detail on an enlarged scale in Figures 16-19. As shown in Figure 16, each collar comprises an inner angle member mm, and a vertical, outer plate I381), continuously welded thereto and braced by triangular pieces I380, thereby providing a marginal channel I38d which cooperates with a hood, described below, to provide a substantially gas-tight seal for each roll chamber.

As shown in Figures 11 and 12, the upper casing I35 and the horizontal base I31 for the collar I38 are recessed at I39 to provide spaces for the reception of water-cooled roll shafts hereinafter described. Likewise, the collar I38 (Fig. 15) has an upwardly projecting recess I 33', formed by a vertical plate I38e and a semi-cylindrical plate I38], providing a rounded bump in the channel I38d, directly above the recess I39, when the parts are assembled.

The roll chambers I3I, I32 are closed by hoods or caps I40, shown more particularly in Figures 7, 18, 19 and 20. Each hood comprises side and end walls I4 I a curved top wall I42, suitably reinforced by angle straps I43 carrying lifting eyes I44, and a refractory brickwork lining I45 for the top and sides. The sides and end walls of each hood carry outwardly and downwardly projecting flanges continuously welded together and to the hood and providing a sealing skirt I46, having a free edge adapted to be received in the channel I38d of the collar I38, as shown in assembled relation in Figures 2 and 3. The end walls of the hoods, at opposite points, are recessed upwardly at I41 to provide a space aligned with the recesses I39, I39, to accommodate the water-cooled roll shafts previously mentioned. A semi-cylindrical plate I41a (Fig. 20) defines the recess andis positioned to embrace the shaft.

Rolls I50, I5l (Figs. 1, 2, and 4) are fixed to hollow shafts I50, I5I', journalled in outboard bearings I52, I53 carried by the upper, horizontal frame members I". The spaces between the shafts and the arcuate recesses I38, I39 and I41 of the roll housing structures are closed by packing glands I52, I53 (Fig. 4), bolted to the ex-- terior face of the casing wall extensions I35 and the collars I38, bolt holes I35a being provided for that purpose (Figs. 14 and 15).

As stated above, the shafts I50, I 5I' are hollow for the circulation of cooling water through suitable connections at their ends, not shown. As the description of the present invention progresses, it will be apparent that many parts of the apparatus are water-cooled, but the cooling water circulating pipes have been omitted from the drawings, since they would only tend to obscure other parts.

Below the horizontal platform II8, there is a roll casing, representing generally at I55 in Figures 1 and 9. The casing comprises a floor member I55a, supported upon transversely disposed I-beams I58 and spaced, longitudinal girders I58a. Side walls I 551), and walls I550 and a ceiling I55d, provided with suitable openings I 55c and a refractory, brickwork lining I51 are supported from the floor I55a. An access door I58, provided with a suitable refractory lining, is mounted for swinging movement in a manner similar to the door shown in Figure 8, whereby the casing may be inspected and cleaned.

The spaces between the casing walls and the brickwork lining I51 is filled with insulating majournalled in bearings I18, I19.

terial 151a. The front. end wall? I550 is made up of a plate bolted to the. reinforced. margins of the casing surrounding} an opening: at, that end. The plate may beremoved: and theinsulation at that end broken down, if it is desired to remove the large roll from the interior of. the casing for replacement or repairs.

Both end wallsv of the casing; I55 are apertured and provided with stufling; boxes I59 (Fig. 10), through which the hollow, water-cooled shaft I of the. lower roll- I 8| projects, the shaft being journalled in outboard bearings I82 carried by suitable supporting brackets I83 mounted on the I-beams I58. Cooling water from a suitable header is conducted by suitable pipes through connections, not shown, to the hollow shaft, to maintain the same in reasonably cool condition.

Projecting through a stufling box I84 secured to the end casing plate I550, is a shaft I85, supported at its opposite end in an appropriate bearing in the opposite end wall, and carrying a scraper blade I88, which projects downwardly into contact with the periphery of the roll I8I, to scrape any scale or dirt therefrom, so that a clean roll surface is always presented to the incoming strip of sheet metal. On its outer end, the shaft I85 carries an operating handle I81, whereby the position of the blade I88 and the tension with which it is urged downwardly onto the surface of the roll may be accurately determined, The blade is preferably a resilient, special alloy plate, substantially of an inch in thickness, known in the trade as "resistal #7.

Beneath the roll casing I55 there are a pair of rolls I88 journalled on appropriate bearings adjacent the opposite ends of the spaced longitudinal girders I58a, whereby, upon occasion, the strip may be led over the roll 18 and under the rolls I88, to by-pass the annealing furnace entirely.

Disposed beneath the platform H8 and in substantial alignment with the final heating chamber I30, there is a second roll housing I10, having rolls therein adapted to guide the strip from the final heating chamber to the first cooling chamber. As shown in Figure 9, the housing I10 has an upper section "I communicating through a water-cooled chute section I12 with the opening in the platform I I8 which is aligned with the slit I30a in the furnace floor I20. A roll I13, disposed in the upper section "I, is fixed to a hollow, water-cooled shaft journalled for rotation in outboard bearings I14 carried by brackets secured in vertical channels I14 extending between supporting I-beams I82 and the furnace platform. Appropriate stuffing boxes surround the roll shaft to prevent the escape of gas. The sides of the casing are provided with suitable water-jackets I15, I15a, the latter of which is extended horizontally at I1-5b over the top wall of the casing proper. The strip is guided under the roll I13 and thence about lower rolls I18, I11, similarly The bearings I18, like the bearings I14, are supported by the vertical channel I14, while the bearings I19 are carried by brackets I11. A dirt catching trough I13 extends lengthwise of the casing below the roll I13 and above the roll I18, to prevent the entrance of dirt or scale between the strip and the periphery of the latter roll. The side and end walls of the casing likewise are water-jacketed, as indicated at I80, I8I, to maintain the rolls in reasonably cool relation and to extract heat from the strip passing throughthe casing. The casing 7 I is supported by suitable I-beams I82 or the like.

The cooling section of the apparatus comprises a vertical frame including upright structural members 511, a pair of upper horizontal I-beams II'Ia, transverse members II1b, and intermediate transverse members 1c. The upper frame members I I11) and I I1c support two pairs of casing assemblies, providing four similar roll housings I95, I 95a, I 95b and I 950, each of which has communication with a pair of vertical chutes. The first housin I95 preferably is provided with outboard bearings I98 (Fig. 4) for a hollow, water-cooled shaft I96, carrying the roll in that housing. The shafts for the rolls in the other roll housings may have bearings I91 associated with the end walls of the housings, since they need not be water-cooled. Each pair of housings I95, l95a and I 95b, I950 is mounted upon an individual base I88, supported on the I transverse frame members II1b and II1c.

Certain of the cooling chutes are supported by roll housings 200, 200a, 2001) (Fig. 1), each of which is made up of two sections similar to the casing section I10a of the roll housing I10. The first casing 200 is provided with outboard bearings 20I for the hollow water-cooled roll shaft, while the other two may have bearings 202 carried directly by the casing end walls.

The strip passes under the roll I11 and is drawn upwardly through a casing section I10a, which, at one side, is bolted, with a suitable gasket interposed, to the casing I10 and at its upper end I10b is provided with a fiange which may be similarly bolted to the lower end of a first watercooled, cooling chute section I85 (Fig. 1).

The strip passes from the cooling chute section I85 over a guide roll in an upper casing I95 to a second cooling chute made up of sections 203 arranged end to end, and from this section through a casing 200 at the lower end thereof to another cooling chute made up of similar sections 203, arranged end to end. The sections 203 may be cooled by the exposure to external atmosphere alone, or may have water jackets associated therewith. At the upper end of the last mentioned section, the strip passes through a casing I95a and then successively through cooling chutes 2I0, 2H, and 2I3. It will be noted that these sections are connected together by casings 200a. I95b, 20% and that a casing I950 is connected to a final chute 235.

The chutes 2I0, 2II, 2I2 and H3 are made up of sections having devices associated therewith for cooling the atmosphere in the chutes and for positively circulating the same over the surfaces of the strip passing therethrough. Prefera-bly, these devices take the form of cooling units 2 I 9, carried by the chute sections and constructed in accordance with the specific disclosure of Figures 41 and 42 of our patent and application identified above. Since the cooling units are not claimed in this application, their details of construction will not be described herein.

If desired, one or another of the cooling and gas circulating assemblies may be removed from its associated chute and a simple fiat plate, or a water-jacketed plate, substituted, depending upon the rate of cooling desired. In the alternative, one or another of the fans may be disconnected and rendered inoperative, to decrease the cooling effect of that section. Moreover, the speed of rotation of the fansand the volume of flow of cooling water through the cooling coils may be independently varied at will, to control the effective cooling of'the various sections.

A preferred drive for the fan units is shown in Figure 1. Certain of the transverse channel members 201, 201a, etc., carry upwardly projecting brackets 400 having bearings I at their upper ends, in which one or another of the shafts 402 are journalled. The transverse channel members also support motor brackets 405 carrying motors 406, connected to the shafts 402.

As indicated in Figure 1, each shaft 402 drives a bank of eight fan units, by means of sprockets 401 and upwardly and downwardly extending sprocket chains 408, 409, trained about similar sprockets H0, 4 on the fan shafts. The upper chains 408 incline upwardly and rearwardly from the axis of the shaft 402 to the axis of the several fans in the upper fan casings, while the lower sprockets 409 incline downwardly and rearwardly toward the sprockets associated with the lower fans.

Thus, the twenty-four fan units in the arrangement disclosed in Figure 1 are arranged in three banks of eight units each, and three driving assemblies and motors serve to drive them all.

The final cooling chute 235, which is disposed behind the vertical I-beam 5a in Figure 1. comprises a plurality of sections similar to the sections 203 which are cooled by room air alone.

A roll seal assembly, generally similar to the one shown in Figures 21-23, but omitting the means for introducing controlled amounts of air, as hereinafter explained, may be suspended from the lowermost chute section 235 or from the transverse supporting channels 2 (Figure 1). Since this assembly is substantially identical to the assembly 245 carried by a downwardly projecting water-jacketed throat 245 associated with the first heating section I21 (Figure 9) of the annealing furnace, only the latter roll seal assembly will be described, reference being had particularly to Figures 21-23.

Each seal assembly includes an upper housing member which is preferably a unitary casting including side walls 241, 248, upper attaching flanges 249 and end walls 250. The end walls 250 terminate in outwardly projecting wings 25!, to which roll supporting brackets 252, 253 may be attached, the former being a, stationary roll bracket, secured by four bolts 252', and the latter being a movable bracket pivoted for limited swinging movement about the axis of an attaching bolt 254. Rolls 255, 256, fixed upon shafts 251, 258, are journalled in bearings 259, 280 carried, respectively, by the fixed and pivoted roll supporting brackets. The brackets are provided with downwardly projecting arms .26I and 252, connected together by an adjustable link 263 and a tension spring 284, whereby the movable roll supporting brackets and the roll 255 are urged constantly toward the stationary brackets and the fixed roll 255.

The downwardly projecting side flanges 241, 248 of the main housing carry elongated sealing bars 288 of hard packed felt, or the like, urged downwardly into contact with the roll periphcries by compression springs 251, surrounding bolts 258 depending from the flanges 249 and interposed between nuts 289 and shoes 210. The bars 286 are pressed inwardly into firm sealing contact with the flange 241, 248 by presser strips 2 and compression 212, surrounding bolts 213 and urged inwardly by nuts 214. This construction provides a substantially gas-tight seal between, the sides of the strip and the rolls and between the rolls and ?the side walls of the main housing.

A seal is effected between the end walls 250 of the housing-and the rolls I255, 256 by hard, pressed felt, end dam members 215, urged inwardly toward the outer faceof the end walls by presser plates 21-6. .The .end :dams 215 and the plates 21!; are provided with arcuate cut-out corners 211, 218, in peripheral engagement with reduced end portions 219 .of the rolls 255, 256. These members are supported by bolts 28!! and are urged inwardly against the end faces 283 of the rolls 255, 2561bysprings28l and .nuts 282.

Hence, a substantially gas-tight seal is provided. The only space through which gas may pass is the-small space between the rolls 255, 256 at the ends thereof, between the strip passing through the rolls and the end dam members.

As stated above, one of the principal objects of the invention of the present application is to burn off the oil applied to the surfaces of thestrip steel during the .cold rolling operation, to clean the strip and to assist in maintaining the desired high temperature in the heatin chamber. This burning 'of the palm oil is made possible by the introduction of sufiicient air to support combustionof the highly heated and volatilized oil. If :air is not so introduced, the strip will be cleaned by volatilization of the oil, but the oil will be broken down into hydrocarbon gases and .amorphous carbon, which collects in the first leg of the furnace and which must be removed from time .to time. Although this removal of the carbon may .:be effected quite simply, by introducing relatively large volumes of air into the furnace and maintaining the electric heating elements energized, thereby burning out the carbon deposit, the delivery of strip to the furnace must be discontinued while the carbon cleaning operation is going on, thereby causing an interruption in the production of annealed strip steel.

We have discovered that, by continuously introducing a controlled amount of air, the palm oil .may be volatilized and cleanly burned as the strip steel is continuously delivered to the apparatus, thereby avoiding the necessity for shutdowns to clean the furnace. Moreover, if the air so introduced is accurately controlled, the nonoxidizing character of the atmosphere in the furnace is not adversely affected, and the heat from the burning oil is utilized to assist in maintaining the desired temperature in the furnace, thereby decreasing the consumption of electric current.

The air may be introduced directly above the roll seal assembly at the entrance end of the apparatus, for instance, by a pipe extending into the water cooled throat 246 (Figure 9) or by a pipe or hose 290 connected to a nipple 29| of accurately predetermined internal diameter in the end wall 250 (Figs. 22 and 23) of the upper housing member for the roll seal. With an apparatus of the size and capacity contemplated and described in this application, a one-quarter inch orifice supplied with air under eight pound pressure per square inch, delivers the right amount of air to burn off the oil on the strip. The conduit 290 may lead from a pressure regulater 292 and a storage tank 293, supplied with air under pressure by a compressor 294. Air at eight pounds pressure forced through a onequarter inch orifice in this manner will be delivered to the heating chamber at the rate of nineteen cubic feet per minute. Strip steel of the gauge employed in the manufacture of crown closures and can ends, between 29" and 31" in width, carries between .and lbs. of palm oil per ton. If theapparatus is operatingat about ten tons of steel per hour (three hundred and thirty lbs. per minute) this amount of air will efficiently support combustion of the oil.

An analysis of the atmosphere in the heating chamber is as follows: CO-16.1%; Cos-3.8%; O-0.-0%. In the cooling chamber, the atmosphere has the following analysis: CO'-12.9%; CO25.1%; 0--0.0%.

The temperature increase in the first ten zones of the annealing furnace, resulting from the burning of the palm oil by the introduction of air is indicated in the following table:

Temp. Zone No. Air 01f Air 0n Increase F. 1, 385 1, 465 +70 1, 430 1, 500 1, 430 1, 490 +60 1, 455 1, 515 +60 1, 535 l, 600 +65 1, 545 l, 610 +65 1, 540 1, 600 +60 1, 470 1, 530 +60 1,590 1, 645 +55 1, 660 1, 725 +65 Except for the means for introducing a controlled amount of air, the only difference between the two gas-tight roll seals at the entrance end of the annealing furnace and at the discharge end of the last cooling chute is that the rolls 255, 256 of the entrance assembly are steel, while at the outlet, it is preferred to use tightly packed cloth disc rolls. Rolls of the latter type consist of a plurality of circular, radially disposed cloth discs threaded on an axial shaft and subjected to axial compacting pressure. Since such rolls are known in the art, they are not shown specifically herein.

In some cases, it has been found desirable to positively drive the rolls 255, 256 at the entrance end of the apparatus, since the strip at that time is coated with palm oil and is quite slippery. To this end, the roll shafts may be provided with intermeshing pinions, to cause the rolls to move in unison, and one .of the shafts may carry a pulley 251', driven by a belt 251a, trained about a pulley 25'") carried by the first guide roll 16 (Fig. 9).

All of the various individual parts of the casing sections, chute sections, roll housing sections and the like are preferably welded together with continuous welds to provide gas-tight seams. The individual sections in turn are preferably bolted together with gaskets interposed between the joints, so that the apparatus, as a whole, is substantially gas-tight. When it is necessary to remove one part from another, or otherwise to disassemble the apparatus, the bolts may be readily removed and the sections taken down.

As a result .of this construction, leakage of gas from the interior of the furnace and from the cooling chutes is reduced to a minimum. The gas-tight roll seals likewise prevent substantial dissipation of gas, while permitting a rapid delivery of the strip into and out of the sealed chambers. A suitable non-oxidizing, hydrocarbon gaseous atmosphere is maintained by continuously delivering a supply of such gas to the interior of the furnace, preferably through four pipe connections, one leading to each heating chamber adjacent the lower end thereof, on the opposite. face of the furnace from that shown in Figure 1, as indicated at 1210, mm, i290, and I300 in Figure 2. It has been found satisfactory to maintain the gas in the annealing apparatus at a pressure between .2 and .5 inch of water above outside atmospheric pressure. The atmosphere of non-oxidizing gas, maintained in the heating and cooling chambers, may be produced by burning clean fuel gas with an insufficient supply of air in a combustion chamber independent of, but in controlled'communication with, the chambers. It is important that the gas be thoroughly dried before it is piped to the heating and cooling chambers. A suitable composition of the gas, as pointed out in the application and patent identified above, comprises: CO: -6%; C0-10-12%: Ha--13%; Na-balance. Obviously, the composition may be varied -as desired between wide limits, so long as a nonoxidizing atmosphere is maintained, to prevent oxidation of the surfaces of the highly heated strip.

Referring to Figures 3 and 5, the strip is heated during its passage through the chambers by radi-' ations from a plurality of banks of radiant electric heating elements "I, 3000. and also by the highly heated atmosphere in the chambers. As shown in Figure 5, the heating elements are preferably arranged in banks comprising four rows of loops or festoons, each constituting a series continuation of the next. One row of festoons 3| is supportedv by hanger lugs 302 comprising integral projections associated with insulator blocks, built into the brickwork of the furnace. Each series of blocks, in the arrangement shown, includes seven triple hanger blocks, each having three lugs thereon, and one single hanger block. An important feature of the heating elements is that the festoons gradually and progressively increase in length from opposite ends toward the middle. For instance, the middle loops may'be substantially 6.6", while the end ones are 3.8", measured from the top of the hanger lugs to the bottoms of the festoons. Each series may include twenty or twenty-one downwardly projecting loops and the loops may be formed from the .128" by 1" NiCr ribbon.

The variation in the lengths of the loops prevents overheating of the edges of the steel strip being annealed and provides a substantially uniform temperature gradient entirely across the strip. Preferably, the longer loops 305 at the center of each series are positively maintained out of contact with each other by guiding projections or lugs carried by special insulating guide blocks 304, mounted in the furnace wall, below the hanger blocks.

The heating elements are arranged in banks of four rows of festoons, connected in series at their ends by continuatlons 308, 301, and 3", the elements and supporting and guiding means of each row being of the same construction. The ends 3N of the heating elements project rearwardly through the furnace brickwork and insulating material, where they are doubled back upon themselves, as at 3 (Figure 6) and welded together and welded to the bifurcated end ll! of a binding post lit, the latter being carried by an insulating plate 3H secured to the furnace casing by bolts 3l5 or the like, in gas-tight relation with an appropriate gasket interposed between the plate and a reinforcing strip 3 I 6 welded to the casing around the opening for the binding post. The binding post 313, which is preferably of Monel metal, has a Monel collar til welded thereto, carrying a plurality of pins 3" projecting into sockets formed in the insulating plate 12 ill, to prevent twisting of the post and the heating element when the post is clamped to the insulating plate by a nut III, or when a bus bar or the like is bolted to the outer .end of the post by nuts Ill.

It will be understood that similar banks III, of heating elements are mounted on both side walls of each heating chamber on opposite sides of the strip steel being drawn therethrough. Each bank, similar to that shown in Figure 5,

and comprising four rows of loops, will be con-' nected in series, by external connections to the corresponding bank on the opposite side of the strip steel. Each pair of banks thus connected constitutes a single heating zone. As pointed out in the application and patent identified above,

'the elements constituting each zone are connected inparallel to a source of current, and individual control means are provided for each zone. A pyrometer tube 325 is provided for each zone, projecting through the furnace end wall between the middle rows of elements, as shown in Figure 5 and as indicated by the dotted circles 325 in Fi ure 2.

Each bank of heating elements in the heating chambers I21, I28 and II! has a 30 kilowatt rating, so that, in each chamber, eight 60 kilowatt heating zones areprovided, In the final chamber I30, the elements are constructed of inch ribbon, with the result that each bank has a 20 kilowatt rating, thereby providing a plurality of 40 kilowatt zonesfs Preferably, in the final heating chamber there are only four such zones.

By connecting the elements of different zones in various ways, as for instance, by connecting all of the elements of two or more zones in series with each other, or by disconnecting some of the elements entirely by the control devices, appropriate heating conditions for a wide variety of gauges and widths of strip can be effected.

We claim:

1. An apparatus for continuously cleaning the oil from the surfaces of cold rolled strip steel and for continuously annealing the strip, comprising heating and cooling chambers in communication with each other, substantially-gastight seals at the entrance and discharge ends of the chambers, means for drawing strip through the seals and the chambers, means for maintaining a non-oxidizing atmosphere in the chambers, and means for burning the oil from the strip in the heating chamber, the last-mentioned means comprising an orifice of predetermined size communicating with the interior of the heating chamber, an air line leading to said orifice and means for delivering air to the line at a predetermined constant pressure, whereby air is delivered to the heating chamber at a controlled rate to support combustion of the oil and to assist in maintaining the temperature in the heat-. ing chamber at the desired elevation.

2. An apparatus for continuously annealing strip steel and for cleaning the cold rolling lubricant from the surfaces thereof, comprising a plurality of parallel, interiorly communicating, vertically disposed heating and cooling chambers, means for guiding the strip into, through and from the chambers, means for introducing nonoxidizing gases to the chambers to produce a nonoxidizing atmosphere therein, sealing means at the entrance and exit ends of the chambers for preventing the admission of atmospheric air as the strip enters and leaves, heating means in heating chambers, cooling means in cooling chambers, an orifice of accurately predetermined size opening into the first chamber above the seal, and means for delivering air to and through the orifice under predetermined pressure, whereby sufficient air is introduced to support combustion of the lubricant in the first heating chamber, without destroying the non-oxidizing character of the atmosphere. I

3. An apparatus for continuously annealing cold rolled strip steel and for cleaning the lubricant from its surfaces, comprising elongated intercommunicating heating and cooling chambers through which the stripis drawn, a gastight seal at the exit end of the cooling chamber, and means for preventing the inadvertent admission of air at the entrance end of the heating chamber and for continuously delivering thereto,

' air at an accurately controlled rate, the last mentioned means comprising a casing communicating with the heating chamber and having side and end walls defining a passage through which the strip is drawn, a roll aligned with and journalled for rotation on a fixed axis below one side wall, a second roll aligned with and journalled for rotation below the other side wall and mounted for limited movement toward and from the first roll, means for urging the second roll toward the first, sealing means between each side wall and the associated roll periphery and between the casing end walls and the rolls, whereby air is prevented from entering the chamber with the strip passing between the rolls, an orifice of predetermined size through one of the walls of said casing, and means for delivering air under accurately controlled predetermined pressure through the orifice and into the casing above the rolls to support combustion of the lubricant on the strip.

4. For use with a continuous annealing apparatus of the type com-prising heating and 0001-4 ing chambers through which the strip steel is drawn, means for preventing the inadvertent admission of air with the strip at the entrance end of the chamber and for delivering air at an accurately controlled rate to the chamber to support combustion of the cold rolling lubricant on the strip, said means comprising a casing communicating with the chamber,;a pair of rolls journalled below the casing, sealing strips carried by the casing, spring means for urging the strips into contact with the roll periphery, end dam members carried by the casing, spring means for urging said members into contact with the end faces of the rolls, whereby air is prevented from entering the casing as the strip passes between the rolls, an orifice extending through the casing, and means for delivering air at an accurately controlled rate through the orifice.

5. A substantially gas-tight roll seal for the entrance or discharge ends of a strip annealing apparatus or the like, comprising a casing through which the strip passes, a pair of fixed brackets projecting downwardly from opposite ends of the casing, a pair of movable brackets projecting downwardly from the opposite ends of the easing, fixed and movable rolls journalled respectively in the fixed and movable brackets, resilient means urging the movable brackets and roll toward the fixed brackets and roll, sealing strips carried by the side walls of the casing with their lower faces in contact with the adjacent roll peripheries, end dam members carried by the end walls of the casing with their lower portions in contact with the end faces of the rolls, and a plurality of springs for maintaining said sealing strips and said end dam members in such contact with the rolls.

6. A substantialli gas-tight roll seal for the entrance or discharge end of a strip annealing apparatus or the like, comprising a casing through which the strip passes, a pair of fixed brackets projecting downwardly from opposite ends of the casing, a pair of pivoted brackets projecting downwardly from the opposite ends of the casing, fixed and movable rolls journalled respectively in the fixed and pivoted brackets, resilient means urging the movable roll toward the fixed roll, sealing strips along the lower margins of the casing side walls, means for urging the strips into contact with the side walls, means for resiliently urging the vstrips into contact with the roll peripheries, sealing plates adjacent the lower margins of the casing end walls, and means resiliently urging the plates into contact with saiii end walls and with the end faces of the re s.

7. A substantially gas-tight roll seal for use with the entrance or discharge end of a continuous strip annealing apparatus or the like, comprising a casing having side and end walls defining a passage through which the strip is drawn, a laterally projecting flange at the upper end of the casing for attaching the same to the apparatus, a fixed roll aligned with and journalled forrotation below one side wall, a second roll aligned with and journalled for rotation below the, other side wall and mounted for limited movement toward and from the first roll, means for urging the second roll toward the first, a sealing strip between each side wall and the associated roll periphery, sealing plate means for closing the spaces between the casing end walls and the rolls, and means for urging the sealing strips and the sealing plate means into contact with the rolls.

8. A substantially gas-tight seal for the entrance or discharge end of a strip annealing apparatus or the like comprising a casing through which the strip passes, having vertically disposed, horizontally elongated side walls and relatively narrow, vertically disposed end walls, a pair of rolls journalled below the side walls on horizontal axes parallel thereto, elongated sealing strips carried by the side walls of the casing, spring means for urging the strips downwardly into contact with the roll peripheries, means projecting from each end ,wall of the casing, an end dam member carried by each of the last mentioned means having a sealing face in contact with the adjacent casing and wall and with the adjacent end faces of the rolls, and compression spring means carried by each of the last mentioned means urging the end dam members into such contact.

9. A substantially gas-tight seal for the entrance or discharge end for a strip annealing apparatus or the like, comprising a casing through which the strip passes, having vertically disposed, horizontally elongated side walls and relatively narrow, vertically disposed end walls, a pair of rolls journalled below the side walls on horizontal axes parallel thereto, elongated sealing strips carried by the side walls of the casing, spring means for urging the strips into sealing contact with said walls, spring means for urging the strips downwardly into sealing contact with the roll peripheries, an end dam member carried by each end wall of the casing, and spring means supported by the casing end walls for urging the end dam members axially and in- 1 wardiy into sealing contact with the end walls Number Name I Date and with the end faces of the rolls. 2,087,145 Harris July 13, 1937 WIILIAM B. COOPER. 2,218,354 Keller Oct. 15, 1940 -EDWARD J. SEABOLD. 2,289,753 Capstafl' July 14, 1942 2,319,301 Cool: May 18, 1943 REFERENCES CIT 2,367,174 Renkin Jan. 9, 1945 The following references are of record in the FOREIGN PATENTS me or this patent: Number Country Date UNITED STATES PATENTS 10 114,754 Germany Nov, 1, 1900 Number Name t 417,657 Great Britain Oct. 4, 1934,

814,124 Fish 32 OTHER REFERENCES ga ig: Industrial Furnaces. by W. Trink's, vol. II, puby iished 1925 by John Wiley 0 Sons, 1110., New York,

1,713,485 Alexander May 14, 1929 15 l 1719 793 Alexander July 2 1929 N. Y. pp. 217-218, paragraph entitled Furnace 1'732917 atmosphere in electrically heated furnaces."

auaou Summey Oct. 22, 1929 

